Republican Senate seats after the 2026 midterm elections?

This market asks how many U.S. Senate seats the Republican Party will hold following the November 3, 2026 midterm elections, counting the results of all regular and special elections determining representation in the 120th Congress. Each numbered outcome corresponds to a specific final seat total, with bucketed tails for extreme results (≤47, 45 or less, 57+). Vacant seats without a scheduled 2026 election default to the party of the most recent occupant, and runoffs count toward the attributed seat. The current favourite is exactly 50 seats at a consensus 27.5%, followed closely by the ≤47 bucket at 26.5% and 49 seats at 19.5%. Together, outcomes at or below 50 seats account for the bulk of implied probability, while totals of 53 or more collectively price under 25%. Both listings on Polymarket and Polymarket US roughly agree on the shape of the distribution centred near the low-50s, but they disagree sharply on specific totals. Cross-platform spreads are widest on the two headline outcomes: Polymarket US prices 50 seats at 28.0% versus Polymarket at 13.0% (a 16-point gap), while ≤47 flips the other way, at 11.0% on Polymarket US against 26.0% on Polymarket. The takeaway: platforms broadly concur on a Republican total near 50, but disagree materially on whether the risk skews to exactly 50 or below 47.